Electroplating



United States PatentO Red Bank, N. 1., assignors to Hanson-VanWinkle-Munning Company, a corporation of New Jersey No Drawing.Application November 16, 1956 Serial No. 622,532

6 Claims. (Cl. 204-49) This invention relates to electroplating and,more particularly, to electrodepositing nickel from an aqueous acidicnickel plating bath. The invention is based on our discovery thata-amino N-heterocyclic compounds, when incorporated in a nickelelectroplating bath, particularly in conjunction with varioussulfo-oxygen compounds, are capable of promoting the formation ofexcellent bright and ductile electrodeposits of nickel over a widecurrent density range.

The electrodeposition of nickel from a plating bath containing asulfo-oxygen carrier brightener additive yields deposits of limitedintensity. Moreover, such brightness as is produced using these agentsis obtained only over a limited current density range. When, however, asmall quantity of an oa-amino N-heterocyclic compound is incorporated inthe plating bath together with a sulfooxygen compound, the brightnesscapacity of the bath is extended, and the electrodeposit is 'ductile andbright over a very wide current density range.

The common structural feature of these. u-amino-N- heterocycliccompounds is the presence of an amino group on an unsaturated carbon ina position alpha to the heterocyclic nitrogen atom, as represented bythe following structural formula: I r

Only relatively small quantities of the a-amino N-heterocyclic compoundsare required in the plating bath, especially when they are used inconjunction with sulfooxygen carrier brightener, forwe have found thatthe highly polarized spatial configuration of an ot-amino N-heterocyclic compound appears to exert a pronounced synergistic eifecton the brightening capacity of the sulfooxygen compound. In general,concentrations of the ocamino N-heterocyclic compound as loW as 0.005gram per liter are effective, but in many cases at least 0.08 gram perliter should be employed to secure the full benefit of their presence inthe bath. Increasing the concentration of these amino compounds mayproduce brittle and perhaps cloudy deposits, and hence there is noadvantage generally in using more than 1 gram perliter, and in mostbaths substantially full benefit of their presence is achieved with 0.3gram per liter or less.

Any a-amino N-heterocyclic compound which is capable of being dissolvedby acid and does not undergo decomposition upon protonation may beselected for inclusion in the plating solution. We have obtainedparticularly satisfactory results by using a carbon-nitrogenheterocyclic compound having an aromatic six-membered cyclic nucleuscontaining from 1 to 3 nitrogen atoms and at least one amino group.attached to a carbon atom in a position alpha to the heterocyclicnitrogen. The basic ring structure for such a-amino N-heterocycliccompounds may be chosen from pyridines, pyridazines, pyrimidiues,pyrazines, and 1,3,54riazines.

A preferred process according to this invention for producing brightnickel deposits comprises electrodepositing nickel from an aqueousacidic solution of at least one nickel salt, in which there is dissolvedfrom about 2,839,459 Patented June 17, 1958 0.08 to about 0.3 gram perliter of a nitrogen-containing heterocyclic compound of the groupconsisting of:

(a) a-Aminopyridines having the structure (b) a-Aminopyridazines havingthe structure NH: R1

(d) a-Aminopyrazines having the structure N N H: and

(e) a-Amino-1,3,5-triazines having the structure I R LN/ NH:

in which Z is a substituent selected from the group con sisting ofhydrogen and Z-pyridyl radicals,and R and R are substituents selectedfrom the group consisting of hydrogen, amino, methyl, ethyl, and propylradicals. The synergistic eitect of these compounds on the brighteningcapacity of various sulfo-oxygen compounds is especially pronounced whenthey are used in the nickel plating solution together with from about Ato about grams per liter of a water-soluble sulfo-oxygen compound of thegroup consisting of unsaturated aliphatic sulfonic acids, mononuclearand binuclear aromatic sulfonic acids, heterocyclic sulfonic acids,mononuclear sulfinic acids, the alkali metal, ammonium, magnesium, andnickel salts of said acids, and mononuclear aromatic sulfonamides andsulfonimides.

Preparation of the a-amino N-heterocyclic compounds may be effected by avariety of standard organic reactions. For example, the a-aminopyridinesmay be prepared by heating pyridine or an alky -substituted pyridinewith sodamide, since the sodamido ion attacks the pyridine nucleus atthe carbon atom alpha to the ring nitrogen. One general technique whichis useful in preparing all of the u-amino N-heterocyclic compounds isbased on initialy forming the a-carboxamide of the: N-heterocycliccompound. Upon treatment with sodium hypobromite, the carboxamideundergoes decarbonylation to form the corresponding OL'aInlnON-heterocyclic compound.

Examples of the ooaminopyridines, ot-aminopyridazines,,a-aminopyrimidines, ot-aminopyrazines, and aamino-1,3,5-triazines, whichmay be used successfully in embodiments of this invention are listed inTable I. Although these oa-amino N-heterocyclic compounds may be used inconcentrations as high as one gram per liter, or even more, there is noparticular advantage to be gained from the higher concentrations, andthey are preferably TABLE I Alpha-amino N-heterocyclic compoundsCompounds R1 R2 R3 R4 Z (1) a-Aminopyridincs Ra- R1 R4- NH-ZZ-aminopyridine H H H H H 2-amino-3-methylpyridine .7 CH H H H H2-ammo-4-n1cthy1pyridine H CH H H H 2-amin0-5-methylpyridine .7 H H3 CHH 1-]. 2-amin0-6-methylpyridine H H H CH H 2-amino-4-ethylpyridine H HCal-l5 H H H 2-amin0-4-isopropylpyridine H C21I5 H H H2-amino-4,fi-dimethylpyridinc.. H CH3 H OH; H H NH? H H H H H H NH; H HH H H Cal-LN amine .7 H CH H H CsHiN 2- (4-aminopyridyl) -2-pyridylamineH NH2 H H csHiN 2,4-diamino-6methylpyridine H NH; H CH3 H (2)a-Aminopyridazines 1 Rr w NHa I N R3 \N/ 3-aminopyridazine H H H3-amino-G-methylpyridazine H H CH3 3-amino-6-ethylpyridazinc M H H C11,; 3-amino-fi-isopropylpyridazine H H C3H1 3,6-diaminopyridazine H HNH (3) a-Aminopyrimidines 2-amjnopyrimidine H H H2-ami110-4-methylpyrimidine H H CH 2-a min0-4,6-dimethylpyrimi- (11110CH3 Ii CIL; 2-amino-3-ethylpyrimidine H H C2115 2,6-diaminopyrimidine NHH H 2,6 diamino 3 mcthylpyrimi dine NHQ CH H 2,6 diamino 4 methylpyrimidine is NHZ H CH (4) a-Aminopyrazines N R R1 R3 N NH2 2-aminopyrazin H HH 2-amin0-5-mcthylpyrazine H CH H 2,6-diaminopyrazinc H2,3-diaminopyrazinc NH H 2-amino-5,6-dimethylpyr2-amino-3,5-dimethylpyrazine (5) a-Amino-1,3,5-triazines I L H RrLN N 22-amino-1,3,5-triazine H H 2,4-diamino1,3,5-triazinc H NH 2,4 diamino 6methyl 1,3,5

triazine CH3 NH? v c 2-ami110-4,6-dimethyl-1,3,5-

triazine CH CH 2-a1nin0-4,6-diethyl-1,3,5-trifiZl-HQ C2115 C2111; a a aa The compounds listed in Table II are examples of sulfo-oxygencompounds which, when used in the plating bath in combination with theii -amino N-heterocyclic 4 compounds, extend the current density rangeover which the formation of bright and ductile nickel deposits may beobtained. These sulfo-oxygen compounds may be used over a very widerange of concentrations (M1, to 80 grams per liter), but preferably areused in an amount in the range from about 1 to about grams per liter.TABLE II Organic sulfo-oxygcn compounds -(1) Unsaturated aliphaticsulfonic acids, and alkali metal, ammonium, magnesium, and nickel saltsthereof: Sodium vinyl sulfonate, H CCHSO Na Sodium allyl sulfonate, HCCHCH SO Na (2) Mononuclear aromatic sulfonic acids, and alkali metal,ammonium, magnesium, and nickel salts thereof: Benzene monosulfonicacid, C H SO H Sodium benzene monosulfonate, C H SO Na Nickel benzenemonosulfonate, (C H SO Ni Sodium p-toluene monosulfonate, CH C H SO Nap-Chlorobenzene sulfonic acid, ClC H SO I-I .Sodium p-chlorobenzenesulfonate, ClC H SO Na Sodium p-bromobenzene sulfonate, B1'C H SO NaSodium p toluene sulfinate, CH C H SO Na magnesium, and nickel salts arein all (4) Mononuclear aromatic sulfonamides and sulfonimides Benzenesulfonamide, C H SO NH p-Toluene sulfonamide, CH C H SO NHo-Sulfobenzoic imide, CtlH4C ON HS 0 2 Benzyl sulfonamide, C I-I CH SONH Benzene sulfhydroxamic acid, C H SO NHOH N,N-dimethyl-p-toluenesulfonamide,

(zu c mso iucn, N,N-dicarboxyethyl benzene sulfonamide,

C H SO N C H COOH) 2 (5.) Binuclear aromatic sulfonic acids, and alkalimetal, ammonium, magnesium, and nickel salts thereof:

Z-naphthalene monosulfonic acid, CmI'IqSOgli 1,5- or 2,7-naphthalenedisulfonic acid, C H (SO H) Nickel 1,5- or 2,7-naphthalene disulfonate,

Sodium naphthalene trisulionate, C H (SO Na) Naphthalene trisulfonicacid, C H (SO H) Diphenyl p,p'-disulfonic acid, HSO C H -C H SO H2-naphthol-3,6-disulfonic acid, HOC iI (SO H) Sodium2-naphthol-3,6-disulfonate, HGC H (SO Na)1-naphthylamine-3,6,8-trisulfonic acid,

(6) Heterocyclic sulfonic acids, and alkali metal, ammonium, magnesium,and nickel salts thereof: Thiophene sulfonic acid, 0 11 860 3 Sodiumthiophene sulfonate, C fi S-SO h-ia 2 -(4-pyridyl)ethyl sulfonic acid, CH I-I-Q H SO I-I For the most part, only free sulfonic acids listed. inTable II. However, the alkali i am? uium,

i the full equivalent of the acids, and may be used in their place incarrying out the process of the invention.

Brightener additions according to this invention have, of course, beenused successfully in the standard Watts nickel electroplating bath.However, these brightener additions are also effective in all othernickel electroplating baths, and consequently the invention isapplicable to electrodeposition from any aqueous acidic plating solutionof one or more nickel salts.

To illustrate the applicability of using the ot-amino N-heterocycliccompounds in different nickel electroplating baths under a variety ofconditions, Table III lists the basic compositions of several types ofplating baths which were employed in carrying out the examples of theinvention that are set forth below.

TABLE III Bath concentrations in grams per liter Bath A Bath B BathNickel sulfate Nickel chloride Nickel sulfamate Nickel tiuoborate"-Boric acid 37. 30 15 EXAMPLE I To the Watts bath (bath A) described inTable III were added 16 grams per liter of sodiumnaphthalenel,3,6-trisulf0nate. A test panel which received a nickelelectroplate from this bath was semi-bright over a wide current densityrange, but exhibited slight haziness in the low and middle currentdensity range. Upon the addition of various concentrations ofrepresentative a-amino N-heterocyclic compounds to this bath,exceptionally bright electroplates were formed in each case over a verywide current density range.

Table IV sets forth in detail the concentrations of specific ct-aminoN-heterocyclic compounds added to a Watts bath (bath A) which alsocontained 16 grams per liter of sodium naphthalene-1,3,6-trisulfonate,and the character of the deposit produced from the bath.

TABLE IV Efiect of a-amino N-heterocyclic compounds on bright nickelplating Identical results were obtained when only 8 grams per liter ofsodium naphthalene1,3,6-trisulfonate were used in the plating solutionin combination with the various ct-amino N-heterocyclic compounds.

EXAMPLE II As a general rule, the effect of the ot-amino N-heterocycliccompounds on the brightening capacity of the bath is more pronounced atthe low and medium current densities. The testpanel of a Hull cellreceived a nickel electrodeposit from Bath A which contained 15 gramsper liter of benzene disulfonic acid. The plated panel was fairly brightexcept at and near the high current density end, when it was streakedand matted. By adding 0.2 gram per liter of 2-aminopyrimidine to theelectroplating solution, the nickel deposit became very bright almostover the entire current density range of the panel. Increasing theconcentration of 2-aminopyrimidine to 0.3 gram per liter did notincrease the brightness nor extend the range further.

EXAMPLE III Brilliant nickel deposits are formed when the a-aminoN-heterocyclic compounds are used in conjunction with aromaticsulfonamides or sulfonimides. Table V summarizes the results obtainedwhen the electroplate was formed from a Standard Watts plating solution(bath A) containing 2 grams per liter of o-sulfobenzoic imide(saccharin) together with varying concentrations of representativeot-arniuo N-heterocyclic compounds.

TABLE V Concen- Compound tration Character (grams) of deposit liter)2-am1no-3-methy1pyridine 0. (l3 Brilliant. 2,2-dipyridylamine 8: E1 g8;0.1. Do. 2-amn1opyr1m1dme 0 Do EXAMPLE IV To a sulfamate plating bath(bath B) which had been properly purified were added 15 grams per literof so dium naphthalene-l,3,6-trisulfonate, and nickel electrodepositedon a Hull test panel at a total current of two amperes per 250 ml. Hullcell. The deposit was semibright over a wide current density range witha strong haze at the middle and low current densities. Upon the additionof 0.08 to 0.26 gram per liter of 2-aminopyridine to this bath, a verybright deposit was obtained over the entire current density range of thetest panel. Similarly, when 0.008 to 0.016 gram per liter of 2,2-dipyridylamine or 0.06 gram per liter of 2-arninopyrimidine was added tothe bath in place of the 2-aminopyridine, an equally brightelectrodeposit was obtained over substantially as wide a current densityrange.

Substitution of 2 grams per liter of o-sulfobenzoic imide (saccharin) inthe sulfamate bath. in place of sodium naphthalene-1,3,6-trisulfonateyielded brilliant electrodeposits when used in conjunction with theaforementioned concentrations of 2-arninopyridine, 2,2-dipyridylamine,and Z-aminopyrimidine.

EXAMPLE V Using a previously purified nickel fiuoborate bath (bath C)which contained 2 grams per liter of o-sulfobenzoic imide, a fairlybright electroplate was deposited on the test panel of a Hull celloperated at 50 C. and a pH of about 3.5. When, however, 0.08 to 0.26gram per liter of 2-aminopyridine was added to the bath, the brightnessrange was substantially increased and a brilliant deposit formed.Similar results were obtained when 0.008 to 0.016 gram per liter of2,2-dipyridylamine and 0.06 gram per liter of Z-aminopyrimidine wereseparately added to the bath in place of 2-aminopyridine.

We claim:

1. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aque ous acidic nickel electroplatingsolution in which there is dissolved from about 0.005 to about 1 gramper liter of an aromatic heterocyclic carbon-nitrogen compound having asix-membered cyclic nucleus containing from 1 to 3 nitrogen atoms and atleast one amino group attached to a carbon atom in a position alpha tothe heterocyclic nitrogen, and from about A1 to about 80 grams per literof a water-soluble sulfo-oxygen compound of the group consisting ofunsaturated aliphatic sulfonic acids, mononuclear and binuclear aromaticsulfonic acids, heterocyclic sulfonic acids, mononuclear sulfinic acids,the alkali metal, ammonium, magnesium, and nickel salts of said acids,and mononuclcar aromatic sulfonamides and sulfonimides.

2. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic solution of at least onenickel salt in which there is dissolved from about A to about 80 gramsper liter of a water-soluble sulfo-oxygen compound of the groupconsisting of unsaturated aliphatic sulfonic acids, mononuclear andbinuclear aromatic sulfonic acids, heterocyclic sulfonic acids,mononuclear sulfinic acids, the alkali metal, ammonium, magnesium, andnickel salts of said acids, and mononuclear aromatic sulfonamides andsulfonimides, and from about 0.08 to about 0.3 gram per liter of anitrogen-containing heterocyclic compound of the group consisting of:

(a) a-Aminopyridines having the structure ([2) a-Aminopyridazines havingthe structure t at (c) wAminopyrimidines having the structure N -Rr (d)tt-Aminopyrazines having the structure lit-H R1 N NHZ and,

(e) otAmino-l,3,5-triazines having the structure wherein Z is asubstituent selected from the group consisting of hydrogen and Z-pyridylradicals, and R and R are substituents selected from the groupconsisting of hydrogen, amino, methyl, ethyl, and propyl radicals.

3, An aqueous acidic electroplating solution of at least one nickel saltin which there is dissolved from about 0.005 to about 1 gram per literof an aromatic heterocyclic carbon-nitrogen compound having asix-membered cyclic nucleus containing from 1 to 3 nitrogen atoms and atleast one amino group attached to a carbon atom in a position alpha tothe heterocyclic nitrogen, and'from about A to about 80 grams per literof a water-soluble sulfo-oxygen compound of the group consisting ofunsaturated aliphatic sulfonic acids, mononuclear and binuclear aromaticsulfonic acids, heterocyclic sulfonic acids, mononuclear sulfinic acids,the alkali metal, ammonium, magnesium, and nickel salts of said acids,and mononuclear aromatic sulfonamides and sulfonimides.

4. An aqueous acidic electroplating solution of at least one nickel saltin which there is dissolved from about Mi to about grams per liter of awater-soluble sulfooxygen compound of the group consisting ofunsaturated aliphatic sulfonic acids, mononuclear and binuclear aromaticsulfonic acids, heterocyclic sulfonic acids, mononuclear sulfinic acids,the alkali metal, ammonium, magnesium, and nickel salts of said acids,and mononuclear aromatic salfonamides and sulfonimides, and from about0.08 to about 0.3 gram per liter of a nitrogen-containing heterocycliccompound of the group consisting of:

(a) ot-Aminopyridines having the structure N Nn-z (b) a-Aminopyridazineshaving the structure (c) a-Aminopyrimidines having the structures (d)ot-Aminopyrazines having the structure (e) a-Amino-l,3,5-triazineshaving the structure wherein Z is a substituent selected from the groupconsisting of hydrogen and Z-pyridyl radicals, and R and R aresubstituents selected from the group consisting of hydrogen, amino,methyl, ethyl, and propyl radicals.

5. The process for producing bright nickel deposits which compriseselectrodepositing nickel from an aqueous acidic'solution of at least onenickel salt in which there is dissolved from about A1 to about 80 gramsper liter of a water-soluble sulfo-oxygen compound of the groupconsisting of unsaturated aliphatic sulfonic acids, mononuclear andbinuclear aromatic sulfonic acids, heterocyclic sulfonic acids,mononuclear sulfinic acids, the alkali metal, ammonium, magnesium, andnickel salts of said acids, and mononuclear aromatic sulfonamides andsulfonimides, and from about 0.08 to about 0.3 gram per liter of ana-aminopyridine having the structure wherein Z is a substituent selectedfrom the group consisting of hydrogen and Z-pyridyl radicals, and R andR are substituents selected from the group consisting of hydrogen,amino, methyl, ethyl, and propyl radicals.

6. The process for producing bright nickel deposits which comprisesclectrodepositing nickel from an aqueous acidic solution of at least onenickel salt in which there is dissolved from about A to 80 grams perliter of a water-soluble sulfo-oxygen compound of the group consistingof unsaturated aliphatic sulfonic acids, mononuclear and binucleararomatic sulfonic acids, heterocyclic sulfonic acids, mononuclearsulfinic acids, the alkali metal, ammonium, magnesium, and nickel saltsof said acids, and mononuclear aromatic sulfonamides and sulfonimides,and from about 0.08 to about 0.3 gram per liter of an waminopyrimidinehaving the structure References Cited in the file of this patent UNITEDSTATES PATENTS 2,644,788 Shenk July 7, 1953 2,644,789 Shenk July 7, 19532,647,866 Brown Aug. 4, 1953 2,658,867 Little -2 Nov. 10, 1953

1. THE PROCESS FOR PRODUCING BRIGHT NICKEL DEPOSIT WHICH COMPRISESELECTRODEPOSITING NICKEL FROM AN AQUEOUS ACIDIC NICKEL ELECTROPLATINGSOLUTION IN WHICH THERE IS DISSOLVED FROM ABOUT 0.005 TO ABOUT 1 GRAMPER LITER OF AN AROMATIC HETEROCYCLIC CARBON-NITROGEN COMPOUND HAVING ASIX-MEMBERED CYCLIC NUCLEUS CONTAINING FROM 1 TO 3 NITROGEN ATOMS AND ATLEAST ONE AMINO GROUP ATTACHED TO A CARBON ATOM IN A POSITION ALPHA TOTHE HETEROCYCLIC NITROGEN, AND FROM ABOUT 1/4 TO ABOUT 80 GRAMS PERLITER OF WATER-SOLUBLE SULFO-OXYGEN COMPOUND OF THE GROUP CONSISTING OFUNSATURATED ALIPHATIC SULFONIC ACIDS, MONONUCLEAR AND BINUCLEAR AROMATICSULFONIC ACIDS, HETEROCYCLIC SULFONIC ACIDS, MONONUCLEAR SULFINIC ACIDS,THE ALKALI METAL, AMMONIUM, MAGNESIUM, AND NICKEL SALTS OF SAID ACIDS,AND MONONUCLEAR AROMATIC SULFONAMIDES AND SULFONIMIDES.